Process of manufacturing urea.



15 the manufacture of to obtain the urea free from 80 lization would be necessary, whereii 45 7 present invention,

50 solution certain UNITED STATES PATENT OFFICE.

HEINRICH IMMENDORI F AND EUBERT, KAPPEN,

F JENA, GERMANYL PROCESS OF MANUFACTURING UREA.

1,018,699. Io Drawing.

"To all whom it may concrn:

Beit known that we, HEINRICH IMMEN- nonrr, a citizen of'Germany, residing at Kaiser-Wilhelm 'strasse 7 ,Jena, in the State of Saxe-Weimar, Germany, professor of a chemistry,

and HUBERT KAPPEN, a citizen of Germany, and residing at lyVestendstrasse 15, Jena, in the State of saxe-Weimaniirermany, chemist, have invented"certain-hew 1o,and useful Improvementsijin Processes of Manufacturing Urea, of which the following is a description.

In the catalytic-treatment of cyanamidby means of certain substances 1n view of urea, it has been found, that the solution in a short time turns alkaline, especially if a high temperature is made-use of. Evidently the alkaline reaction is brought about principally by the formation of ammonia owing to .decomposition of thecyanamid orthe urea. In the alkaline solution of'the cyanamid the formation of dicyandiamid is exceedingly accelerated so that a relatively high quantity of 'dicyandiamid is formed in the process be- The output of urea is ac sides the urea. cordingly reduced, and should it be desired dicyandiamid, very circumstantial operations of regrystallosses of urea are inevitable.

We have found, that the formation of dicyandiamid maybe avoided and urea practically free of dicyandiamid obtained, if the process is carried outwith an acidic solution. Furthermore by employing an acidic solution, the reaction is performed in a substantially shorter time, a fact, which on the other hand, explains tosome extent why the 40 formation of dicyandiamid is avoided in the course ofthe process, as the longer the reaction, the more dicyandiamid is formed. Another advantage of carrying out the process with acidic solution according tothe is that the efliciency of the catalytic substance (catalyzer) is not substantially diminished in he course. of 'the operation. 'In this respect it must be understood that in employing a non-acidic substances contained in so- Speciflcation of Letters Iatent. Application filed July-25, 1911.

' Patented Dec. 31,1912. Serial No, 640,479.

lutions of cyanamid salts or of cyanamid, are precipitated on the catalyzer, owing to the phenomena of adsorption. It'is for in- Examples; I The operation-was carried out, on'the one hand in an acidic solution, and on the other hand with a solution of cyanamid showing neutral reaction in the beginning of the operation and becomin alkaline in the course of the operation. ifi'erent substances were made use of as catalyzers. 2000 ccm. of the solution, containing 2.4% cyanamid nitrogen, were heated with 300 gr. of the catalytic substances. The acidic solution had been acidified with 10 com. of concentrated sulfuric acid.- 7

Time of transfor Time of transformation in a solo: Catalyzer, mation lu acldtlon first neutral.

lc solution. then turned alkallne.

(l) Peroxid of manga- 3h0lll8 7hours.

nese natural manganese ore). (2) Hydroxld of iron 50 minutes 2 hours. (8) Hydroxid 0t chro- 2 hours 20 mln- 4hours.

mium. utes, (4).Dioxid of tin 1 hour...- 2 hpurs 15 minu es.

The'acceleration of the reaction in an acidic solution decreased in the trials (2) and (3) owing to the consumption of acid for the formation of salts of the catalyzer 1n the course of the operation; the solution first acidic became gradually neutral. By replacingthe used up acid in the course of the operation, a further acceleration of the reactlonfmay be realized in such cases.

II. 300 gr. of eroxid of manganese artificially prepared were heated to 85-90 with 2000 ccm. oi. a solution of-cyanamid containing 2.4%;of cyanamid nitrogen, the

solution being tl'iorouglilly stirred during the operation; this trial was made once- Wltll a solution neutral In thebegmning ofthe operationiand becoming alkaline in, the course of the; operation", and then' with a solution acidified by addition of 10 com. of concentrated sulfuric acid. The following results were obtained:

A. With neutral, afterward alkaline solution.

In neutral, afterward alkaline solution the operation took two hours, in acidic solution 20 minutes,-

It has furthermore been found by us, that the formation of dicyandiamid canbe diminished and the output of urea increased to a certain degree,--th0ugh less than in using an acidic solutionif care is taken to maintain the initially neutral reaction of .thc cyana mid solution permanently throughout; the process. This efi'ect obtained by adding gradually during the reaction as much acid as corresponds totli'e alkalinity formed in; the operation. lllxainplz 2000 cent. of cyanamid solution with 1.1.1 mgr. of cyanamid niir cu and 3.10 ingr of dicyandiamidnitrogen in 3 tl'lll. were heated to] with 300 gr. of liyilralcd manganese pe'roxid. The neutral rcaciion was ncrrnanently i1i:tiiitttii;fr=(l by gradual additionof acid during the operation. After one hour the operation was completed: '5 ccm. of the transformed solution contained 5.10 mgr. of dicyandiamid. nitrogen. Hence only about. 2 mgr. of dicyandiamid nitrogen had been formed bcsides the 1irea,wlic1'eas about T-mgr. of dicyandi-amid nitrogen was formed When working in the same conditions with he same solution, but without neutralizing the,

alkaline react-ion.

Peroxid of manganese and may be made use of by preference as catalyzers, as these substances are insoluble in diluted acid and as their'catalytic action is particularly intense. Other suitable catalyzcrs are e 9. tin dioxid, iron oxid,

hydroxid of iron-(especially such iron hydi'oxich as has been made diiticultly, soluble acids by suitable treatment), (and and l'tfi'i'ifOXld of chromium, oxid peronid of its hydrates lead. course a mixture of two or more 'catalyz'ers could also be employed i Any suitable acid may be employed for acidifying. or neutralizing the solution. The effect of the di-tlii'rrent acids.depends.to

degree of dissociation. Sulfuric acid for instance is more cl'licacious thanvacetic acid, nitric acid and hydrochloric acid more than sulfuric acid. .lnstcad' of acids acid salts may also be made use of.

,7) ya 'certaurdcgrec upon the r strength -,or

Trials have shown that a considerable acceleration. of the process can be realized by strongly stirring or shaking the solution together with the 'alalyzer, or by otherwisesuspending or distributing fl thc cata-' lyzer uniformly in the liquid during operation; A similar elfect may beobtained by causing the cyanamid solution to drip over the catalyzer filled into suitable apparatus.

., a Lea. [*urtluzrmore it has been found that-1t was" advantageous, for accelerating the reaction and preventing the formation. of dicyan'di amid, to heat the solution of cyanamid before adding the catalyze), and in general to bring thereacting mixture as quicl ly" as possible to the desired temperature.

In using calciumcyanamid (lime nitrogen) obtained according to a well known process by reacting. with nitrogen gas upon a heated mixture of carbid and ehloridcf calcium, or in' usi-ngisuch solutions of cyan' amid salts as had been neutralized by means of hydrochloric acid for utilization "in the present process, the presence (i'f'ClllOIlCl of calcium 1n the solution is (HHllZU'HLSSHIg IIL asrnuch as chlorid-of calcium combines with the urea to form l'iygroscopic compounds winch are", as Well the urcafisoluble in Water and in alcohol. Owing to this fact, the obtaining of pure urea, that is to'say urea free from calcium chlorid, by means of rccrystallization, reiii'lered practically 'i In-Y" possible in this case. For removing t-li1s'iiiconvenience, there are added, to the solution of urea containing chlorid of calcium, such salts (sulfates; carbonates, nitrates or the like) or other substances, as convert the chlorid of calciuminto salts insoluble in al, cohol. From the mixture of urea and salts so obtained the urea can be extracted free from salts, quantitatively, by means offal-- cohol. V It has been observed that n carrying out the process in a permanently neutralsolution, the efficiency of the catalyzersgradu-.

ally diminishes. This phenomenon is to be ascribed to the fact, that ccrtainsubstances cont-ainedin the solutiomsuch as for instance carbonateof calcium, sulfate of, calcium or the like, are absorbed byehe cata lyzer, that is to say, precipitated upon its surface. In order to regenerate tlmcatalyzer' lessened in its efficiency, it may be,

treated with acids, water or like agents,

the addition of acid.

however be taken to add as much acid as necessary for neutralizing the calcium or sodium base, before giving, in case of operating with an acidic solution, the solution the desired acidity. In the same way-the small percentage of bicarbonate of calcium, always left in solutions of cyanamid obtained from cyanamir of calcium by precipitating the calcium base with carbonic acid, may be destroyed previously by means of the addition of a corresponding amount of acid.

Cyanamid of calcium (lime nitrogen) which is first to be considered for use as primary material in thepresent process, is very slightly soluble in Water, so that it is hardly possible to obtain with the ordinary method a solution containing more than 3% of ey anamid nitrogen. concentrated solutions for the present process, it is advisable to-proceed as follows: The poorsolution obtained in a first treatment of the cyanamid of calcium with water, is freed of the calcium base-by precipitating with carbonic acid, sulfuric acid, oxalic acid or the like. The cyanamid solution free from bases thus obtained is then used for extracting further quantities of cyanamid of calcium, and from the more concentrated solution thus obtained the calcium base is again precipitated. This operation is to be repeated until the desired degree of concentration is realized. Instead of utiliz ing this cyanamid solution freed from bases, the weak solution of urea first obtained in the process, might be made use of for dissolving the cya'namid of calcium and the solutions thus obtained containing a mixture of urea and cyanamid employed again and again in the process, until the desired strength of the urea solution is reached.

The urea produced by the invention described is suitable for the manufacture of other chemical compounds. As it contains none'oronly a small amount of dicyandiamid (which is a poison for vegetables) it can also beempioyed for fertilizing purposes.

What we claim is:

1. The process of manufacturing urea, which consists in treating a solution of cyanamid with suitablecatalyzers and preventing alkaline reaction in the solution by *2. The process of manufacturing urea,

which consists in treating a solution of cyl which In order to obtain more anamid with suitable catalyzers and preventmgalkahne reaction in the solution by the addition of an agent having an acid reaction.

The process of manufacturing urea whichconsists in treating an acidic solution of cyanamid with suitable catalyzers.

i. The process of manufacturing urea, which consists in treating a solution of cyanaluid with suitable catalyzers and'maintaining a non-alkaline reaction of the solution by the addition of acid.

The process of manufacturing urcwhich consists in treating an acidic soluti 1 of cyanamid with a metallic oxid.

(5. The process of manufacturing urea, which consistsin trcating an acidic solution of c anamid with a hydrated metallic oxid.

7. T 1e process of manufacturing urea, which consists in treating an acidic solution of cyanamid with manganese peroxid.

8. The process of manufacturing urea, which consists in treating an acidic solution of cyanamid with hydrated manganese peroxid. I

9. The process of manufacturing urea, which consists in treating a solution of cyanamid with a metallic oxid and maintaining a non-alkaline reaction of the solution by the addition of acid.

10. The process of n'ianufacturing urea, which consists in treating a solution of cy-' anamid with a hydrated metallic oXid and maintaining a non-alkaline reaction of the solution by the addition of acid.

11. The process of manufacturing urea, which consists in treating an acidic solution of cyanamid with a suitable catalyzer and bringing the catalyzer into close contact With the solution during treatment.

12. The process of manufacturing urea, which consists in treating an acidic solution of cyanamid with catalyzers and distributing the catalyzer uniformly in the solution. i

13. The process of manufacturing urea, which consists in treating an acidic solution of cyanamid with catalyzers and distributing the catalyzer uniformly in the solution by stirrin 14. The process of manufacturing urea, which consists in treating a solution of cyanamid with a suitable catalyzer, maintaining a non-alkaline reaction of the solution by the addition of acid, and bringing the catalyzer into close contact with the solution during treatment.

15. The process of manufacturing urea, which consists in treating a solution of cyanamid with a suitable catalyzcr, maintaining a non-alkaline reaction of the solution by the addition of'aci-d, and distributing the catalyzcr uniformly in the solution,

16. The process of manufacturing urea,

consists in treating a solutlon of cy- 5, addition of acid.

1 tin anamid with suitable catalyzers, maintain ing a nonalkaline reaction of the solution by the addition of acid, and distributing the catalyzeruniformly in the solution by stirring.

.17. The process of manufacturing urea which consists in treating with suitable catalyaers an acidic solution of cyanamid, preheated to the reaction temperature.

18. The process of manufacturing urea,

which consists in treating With suitable catalyzers a solutlon of cyana'mid preheated to.

the reaction temperature, and maintaining av non-alkaline reaction of the solution by the 19. The process of manufacturing urea, which consists in treating a solution of cyanamid, preventing alkaline reaction by the addition of acid, with a catalyzer used in former operations, and regenerated by treat- 'ment with suitable solvents.

jivhich consists in treating anamid, preventing alkaline reaction by the addition of acid, with a catalyzer used in former operations, and regenerated by treat- '22. The

.20. The rocess of manufacturing urea,

ment' with suitable acids.

21. The rocess of manufacturing urea,

-which consists in neutralizing an aqueous solution of a cyanamid salt, acidifying the solution With asmuch acid as is necessary for maintaining the acidic reaction permanently during the operation and heating the acidified solution with a suitable catalyzer. recess of manufacturing urea which consists in adding to a solution of a cyanamid salt as much acid as is necessary forneutralizin'g the base of the saltand for destroying soluble bicarbonates contained in the solution, heating the solution with a suitable catalyzer and'adding during the opa solution of cy-- intense eration-as inuch'acid .as is necessary for maintaining a non-alkaline reaction cit the solution 4 v 23. The process of manufacturing urea, which consists treating a solution of cyanamid of calcium, containing chlorid ol' calcium with a catalyzer, preventing alkaline reaction by the addition of acid, adding to the thus obtained solution substances suitable for forming with the blorid oil? calcium salts insoluble in alcohol, and extractingthe urea from the mixture of salts and urea by means of alcohol.

e 24'. The process of manufacturing urea, which consists in preparing an aqueous solution of cyanamid of calcium, removing therein the base by ')recipitating' it by suit able agents and filtering the precipitate, sin-- ploying the thus obtained cyanamid solu tion assolvent for a fresh quantity of cyanamid, removing again from the thus obtained solution the base, and treating the concentrated solution of cyanamid finally obtained with a catalyzer, while at the same time preventing alkaline reaction.

25. The process of manutacturi n'g'urea, which consists in dissolving'cyanamid of calcium in a solution of urea, removing-from the thus obtained solution the base by precipitating it withsuitable agents and filtering the precipitate, and treating the thus" obtained solution with a catalyzer; While 

